1. Field of the Invention
The invention relates to an ink jet recording head and a method of producing the ink jet recording head in which, when a cavity plate and a vibrating plate that are made of plastic are joined to each other by means of fusion, a firm joining is realized and shapes of nozzles and flow paths are maintained.
2. Description of the Related Art
Conventionally, a recording method in which ink is ejected from minute nozzles to adhere to a recording medium such as a sheet of paper is known as the ink jet recording method. As one of the principles of the ink jet recording methods, there is the on-demand ink Jet printing method. Generally, an ink Jet recording head (hereinafter, referred to as "recording head") according to this method has a structure shown in FIG. 5 which is a plan view as seen from the side of grooves of a cavity plate and FIG. 6 which is a section view thereof. Specifically, a vibrating plate 19 is placed on a cavity plate 11 in which plural ink ejection nozzles 12, ejection flow paths 13, ink pressurizing chambers 15, ink supply paths 16, filter flow paths 18, and a common ink reservoir 17 are formed by conducting an etching or machining process on a plate made of glass, metal or the like, and integrated with the cavity plate 11. Piezoelectric elements 20 functioning as electromechanical transducers are then joined through a conductive film 21 to positions of the outer side face of the vibrating plate 19 which confront the ink pressurizing chambers 15, respectively.
In this structure, when a voltage is applied as an electrical signal to one of the piezoelectric elements 20, the vibrating plate 19 is displaced toward the ink pressurizing chamber 15 so that the volume of the chamber 15 is rapidly reduced. An amount of ink corresponding to the reduced volume is ejected from the corresponding nozzle 12 to fly in the form of an ink droplet, and then impacted on an opposing recording sheet to conduct a printing.
In the prior art example, when the cavity plate 11 is, made of a silicon wafer and the vibrating plate 19 is made of a glass plate, the cavity plate 11 and the vibrating plate 19 are joined to each other by an electrostatic joining technique. When both the cavity plate 11 and the vibrating plate 19 are made of plastic, they are joined to each other by a technique in which an adhesive is used or that in which plastic itself is heated to melt and then fused to each other. These joining techniques have a common defect that the joining has a weak durability and hence the flow paths cannot maintain their correct shape and are slightly deformed. Therefore, it has been demanded to develop a joining technique which exhibits a high reliability. In the view points of durability and rigidity, for example, engineering plastics such as polyether imide, polysulfone, polyether ketone, and polyether sulfone have been studied as materials of such a cavity plate and a vibrating plate. Generally, it is difficult to join these materials by an adhesive. Therefore, it has been studied to employ a method in which these materials are joined by means of fusion. Such a joining method using fusion has an advantage that a joining with very high reliability is obtained because there is no adhesion interface of foreign material such as an adhesive, but has a problem that minute ink flow paths formed on the surface of the cavity plate are heat-deformed by heat in the joining process.